As a technique to introduce impurities into a solid sample, the plasma doping method is known for ionizing impurities and introducing the ionized impurities into a solid with low energy (for example, refer to Patent Reference 1). FIG. 9 shows a general configuration of a plasma-processing device used for the plasma doping method as a related art impurity introducing method described in the Patent Reference 1. In FIG. 9, a sample electrode 6 for mounting a sample 9 composed of a silicon substrate is provided in a vacuum chamber 1. In the vacuum chamber 1 are provided a gas supply device 2 for supplying a doping rare material gas such as B2H6 and a pump 3 for depressurizing the inside of the vacuum chamber 1 in order to maintain the inside of the vacuum chamber 1 at a constant pressure. Microwaves are radiated from a microwave waveguide 41 into the vacuum chamber 1 via a quartz plate 42 as a dielectric window. Interaction of the microwaves and the DC magnetic field formed by an electromagnet 43 forms high magnetic field microwave plasma (electron cyclotron resonance plasma) 44 in the vacuum chamber 1. To the sample electrode 6 is connected a high-frequency power source 10 via a capacitor 45 so as to control the potential of the sample electrode 6. Gas supplied from a gas supply device 2 is introduced into the vacuum chamber 1 from gas flow-out holes 46 and is exhausted into a pump 3 from an exhaust port 11.
In a plasma processing device thus configured, a doping raw material gas introduced from the gas inlet 46, for example B2H6 is turned into plasma by way of plasma generating means including the microwave waveguide 41 and the electromagnet 43 and boron ions in the plasma 44 is introduced into the surface of the sample 9 by way of the high-frequency power source 10.
After a metallic wiring layer is formed on the sample 9 on which impurities have been introduced, a thin oxide film is formed on the metallic wiring layer in a predetermined oxidizing atmosphere and then a date electrode is formed on the sample 9 by using a CVD device or the like to obtain a MOS transistor, for example.
In the field of a general plasma-processing device, a plasma processing device including a gate shutter is known (for example, refer to Patent Reference 2). FIG. 10 shows the general configuration of a related art dry etching device described in Patent Reference 2. In FIG. 10, a sample is transferred into the vacuum chamber 1 via the through gate (gate passage) 51 of the vacuum chamber 1 and then the sample is mounted on the sample electrode 6 in the vacuum chamber 1 and plasma processing is made on the sample in the vacuum chamber 1. A reaction chamber 1 as a vacuum chamber includes a cover 52 for preventing the reactive products from being built up on the gate passage 51 by covering an opening at the reaction chamber as an opening of the gate passage 51 in the reaction chamber when a semiconductor wafer as a sample is processed in the reaction chamber 1 as a vacuum chamber. The cover 52 includes a shielding plate 53 and a base seat 54 on which the shielding plate 53 is mounted. The shielding plate 53 is a belt-like thin plate formed along the inner wall 1b of the reaction chamber 1 and having a width dimension larger than the width dimension of the opening at the reaction chamber so as to cover the entire opening at the reaction chamber. A numeral 55 represents a preliminary chamber, 56 a gate valve, 57 a transfer arm, and 58 a driving device. (Description of a component with an asterisk (*) is omitted.)    Patent Reference 1: U.S. Pat. No. 4,912,065    Patent Reference 2: JP-A-10-199957